Two trains travelling in opposite directions cross each other in 25 seconds. If the length of both the trains is 250 m each and the speed of one of them is 45 km/hr, what would be the speed of the other train?

Given:

Length of both trains = 250 m each.

Time taken to cross each other = 25 seconds.

Speed of one train = 45 km/hr.

Formula Used:

Total relative speed = (Combined length of both trains) / (Time taken to cross).

Speed of the other train = Total relative speed - Speed of one train.

Note: Convert speed from km/hr to m/s using the formula: 1 km/hr = 5/18 m/s.

Calculation:

Length of both trains combined = 250 + 250 = 500 m.

Relative speed = Total length / Time

Relative speed = 500 / 25

Relative speed = 20 m/s

Convert speed of the first train from km/hr to m/s:

Speed of the first train = 45 × (5 / 18)

Speed of the first train = 12.5 m/s

Speed of the other train = Relative speed - Speed of the first train

⇒ Speed of the other train = 20 - 12.5

⇒ Speed of the other train = 7.5 m/s

Convert speed back to km/hr:

Speed of the other train = 7.5 × (18 / 5)

Speed of the other train = 27 km/hr

The speed of the other train is 27 km/hr.